The present invention relates to a container comprising a substantially dimensionally stable outer wall and an easily deformable inner pouch into which a pharmaceutical liquid can e.g. be filled that can be discharged with a pump attached to the neck of the container. However, the contents of the container may also be a cream or a past which is discharged from the opening of the container by compressing the outer wall.
The container may have the shape of a bottle or e.g. of a small tube, its shape being not limited in any way.
There are known containers consisting of a substantially dimensionally stable outer wall and an easily deformable inner pouch which are produced, for example, in a coextrusion type blow molding process and consist of two plastic layers that do not establish any connection with each other, i.e., the inner pouch which has first been inflated in contact with the dimensionally stable outer wall of the container detaches from the outer wall when the contents of the container are gradually discharged.
To enable the inner pouch to contract in accordance with the discharged volume, some kind of pressure compensation must take place between the outer wall of the container and the contracting inner pouch. To this end, pressure compensating holes through which air can enter into the space between the outer wall and the inner pouch are formed in the outer wall in the formerly known containers of the type in question.
Although a pressure compensation takes place through the holes in the outer wall, a negative pressure is often created in the inner pouch because a complete pressure compensation along the whole outer circumference of the inner pouch does not always take place and restoring forces are created by the contraction of the inner pouch, with the result that the inner pouch tries to return to its natural form to a certain extent.
The negative pressure prevailing in the inner pouch has, in turn, the consequence that air can enter into the inner pouch, either through fine opening in the wall of the inner pouch or, for example, due to leakage in the area of a possibly existing pump.
The entry of air into the inner pouch is highly undesired because this may deteriorate the quality of the contents of the container and because the liquid level in the inner pouch may fall to such an extent that part of the contents of the container can no longer be discharged, for instance because of the fact that the liquid level falls below the inlet opening of the suction tube of a pump.